Heat pack



FIG. 1 is a perspective view of the heat pack showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The left side, not shown in the figures, is a mirror image of the right side shown in FIG. 4. 

The ornamental design for a heat pack, as shown and described. 